package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.CACHE_SHOP_KEY;
import static com.hmdp.utils.RedisConstants.LOCK_SHOP_KEY;

@Slf4j
@Component
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit){

        stringRedisTemplate.opsForValue().set(key , JSONUtil.toJsonStr(value),time , unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
       redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key , JSONUtil.toJsonStr(redisData),time , unit);
    }

    public <R , ID> R queryWithPassThrough(String keyPrefix , ID id , Class<R> type , Function<ID , R> dbFallback , Long time , TimeUnit unit){
        String key = keyPrefix + id;
        //1.从redis中查询缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isNotBlank(json)){
            //3.存在直接返回
            return  JSONUtil.toBean(json , type);
        }
        //判断命中的是否是空值
        if(json != null){
            //返回错误信息
            return null;
        }
        //4.不存在根据id查询数据库
        R r = dbFallback.apply(id);
        //5.不存在，返回错误
        if(r==null){
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key , "" , RedisConstants.CACHE_NULL_TTL , TimeUnit.MINUTES);
            //返回错误信息
            return null;
        }
        //6.存在写入redis
        this.set(key , r , time , unit);
        //7.返回
        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }

    public  <R , ID> R queryWithLogicalExpire(String keyPrefix , ID id , Class<R> type , Function<ID , R> dbFallback , Long time , TimeUnit unit){
        String key = keyPrefix + id;
        //1.从redis中查询缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isBlank(json)){
            //3.存在直接返回
            return null;
        }
        //4.命中,需要把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData() , type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            //5.1未过期直接返回店铺信息
            return r;
        }
        //5.2 过期,需要缓存重建
        //6.缓存重建
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2判断是否获取锁成功
        if(isLock){
            //6.3成功，开启独立线程实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //重建缓存
                    this.setWithLogicalExpire(key , r1 , time , unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //6，4返回过期商铺信息
        //7.返回
        return r;
    }
}
